Consider the following observations regarding the lifespan of living organisms:
(I) The lifespan of an organism is always strictly correlated with its physical body size. (II) A mango tree exhibits a significantly shorter lifespan when compared to a peepal tree. (III) Parrots and crows show similar sizes, yet their lifespans differ drastically. (IV) Natural death is an absolute certainty for every single individual organism without exception on Earth.
Which of the statements given above are correct?
Lifespans are not correlated with body size, making statement (I) incorrect. Single-celled organisms are considered biologically immortal because they divide to form daughter cells rather than undergoing natural death. Hence statement (IV) is incorrect. Statements (II) and (III) are correct according to NCERT.
Question 2 of 100
📘 CLASS XII
Read the statements below concerning single-celled organisms and select the appropriate combination:
(p) Single-celled organisms undergo cell division, which in itself represents their mode of reproduction. (q) There is no natural death in unicellular organisms because the parent body continues living as its offspring. (r) Binary fission in Amoeba is an unequal division where a small bud remains attached to the parent initially.
Choose the correct option.
Cell division itself is the mode of reproduction in unicellular organisms. Amoeba reproduces by equal binary fission, whereas budding is characteristic of yeast. Therefore, statement (r) is incorrect.
Question 3 of 100
📘 CLASS XII
Analyze these statements regarding yeast and unicellular algae reproduction:
(i) In yeast, the division of the cell is unequal, generating tiny buds that eventually separate. (ii) In Chlamydomonas, reproduction occurs via non-motile microscopic structures called conidia. (iii) Cell division is itself the primary mode of reproduction in Monerans and Protists.
Which of the following is correct?
Yeast reproduces by budding, and Monerans and Protists reproduce mainly by cell division. Chlamydomonas produces motile zoospores, whereas conidia are produced by Penicillium. Hence statement (ii) is incorrect.
Question 4 of 100
📘 CLASS XII
Examine the characteristics of special asexual reproductive structures found in Kingdom Fungi and simple plants:
(a) Zoospores are microscopic, motile structures commonly observed in several algae. (b) Penicillium reproduces asexually through non-motile, exogenous spores called conidia. (c) Gemmules are internal asexual buds typical of freshwater and marine sponges. (d) Buds in Hydra are endogenous structures formed deep within the gastrovascular cavity.
Which of these statements are true?
Zoospores, conidia and gemmules are correctly described. Buds in Hydra are exogenous outgrowths formed on the outer surface of the body wall, not endogenous structures. Therefore, statement (d) is incorrect.
Question 5 of 100
📘 CLASS XII
Identify the correct combinations of plants and their vegetative propagules:
(1) Potato – Eyes (Adventitious buds on modified stem) (2) Ginger – Rhizome (3) Agave – Bulbils (4) Bryophyllum – Adventitious buds arising from notches on leaf margins (5) Water Hyacinth – Runner
Choose the correct option.
Potato, ginger, Agave and Bryophyllum are correctly matched with their vegetative propagules. Water hyacinth propagates through offsets rather than runners. Therefore, statement (5) is incorrect.
Question 6 of 100
📘 CLASS XII
Evaluate the following statements regarding the Terror of Bengal:
(I) It is an invasive aquatic weed known as water hyacinth. (II) It was introduced in India due to its ability to yield edible nutritive tubers. (III) It drains dissolved oxygen from water bodies, which directly causes the death of fishes. (IV) It propagates vegetatively at a phenomenal rate via offsets.
Identify the correct set of statements.
Water hyacinth is an invasive aquatic weed popularly called the Terror of Bengal. It depletes dissolved oxygen in water bodies and propagates rapidly through offsets. It was introduced because of its beautiful flowers and attractive leaves, not for edible tubers. Hence statement (II) is incorrect.
Question 7 of 100
📘 CLASS XII
Read the statements below about the site of origin of plantlets in vegetative propagation:
(x) New plantlets in potato, ginger, and banana invariably arise from modified roots when they touch water. (y) Modified stems have nodes, and when these nodes come in contact with damp soil or water, they produce roots and new plants. (z) Marginal notches of leaves are the exclusive site of vegetative reproduction in Bryophyllum.
Choose the correct deduction.
Potato, ginger and banana reproduce vegetatively through modified stems, not modified roots. Their nodes produce roots and new shoots. In Bryophyllum, adventitious buds arise from the notches along the leaf margins.
Question 8 of 100
📘 CLASS XII
Select the correct statements regarding the adaptive shifting of reproductive modes in simple organisms:
(i) Fungi and algae rely entirely on asexual reproduction throughout their lifetimes regardless of environmental conditions. (ii) Just before the onset of adverse, dry, or cold conditions, simple organisms shift to sexual methods. (iii) Sexual reproduction generates zygospores or thick-walled structures that can survive harsh winters or droughts.
Choose the correct option.
Many algae and fungi reproduce asexually under favourable conditions but switch to sexual reproduction before adverse conditions. Sexual reproduction produces resistant structures such as zygospores that help survival. Hence statement (i) is incorrect.
Question 9 of 100
📘 CLASS XII
Compare the features of asexual and sexual reproduction from the statements below:
(1) Asexual reproduction is rapid, simple, and involves a single parent with or without gamete formation. (2) Sexual reproduction is an elaborate, complex, and slow process. (3) Offspring of asexual reproduction are clones, meaning they can be genetically distinct but morphologically identical to the parent. (4) Offspring of sexual reproduction show variation due to recombination.
Which statements are correct?
Clones produced by asexual reproduction are both morphologically and genetically identical to their parent. Therefore statement (3) is incorrect, while statements (1), (2) and (4) are correct.
Question 10 of 100
📘 CLASS XII
Read these statements about developmental phases in different organisms:
(I) The juvenile phase represents a period of growth and maturity before an organism can reproduce sexually. (II) In plants, the juvenile phase is specifically termed the vegetative phase. (III) The duration of the juvenile phase is constant and identical across all sexually reproducing species.
Choose the correct option.
The juvenile phase is the period before sexual maturity and is called the vegetative phase in plants. Its duration varies widely among organisms, so statement (III) is incorrect.
